code: def test_convert_gray_to_rgb(self):
      # Get MNIST
      (x, _), (_, _), _, _ = load_mnist(raw=True)
      n = 100
      x = x[:n]
  
      # Test RGB
      x_rgb = convert_to_rgb(x)
      s_original = np.shape(x)
      s_new = np.shape(x_rgb)
  
      self.assertEqual(s_new[0], s_original[0])
      self.assertEqual(s_new[1], s_original[1])
      self.assertEqual(s_new[2], s_original[2])
      self.assertEqual(s_new[3], 3)
  
file_path: adversarial-robustness-toolbox/tests/test_visualization.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import os.path
  import unittest
  import numpy
  from art import config
  from art.utils import load_mnist, load_cifar10
  from art.visualization import create_sprite, convert_to_rgb, save_image, plot_3d
  from tests.utils import master_seed
label_desc: Use image node_id 3 for calling the TestVisualization obj's underlying member method code with example usage: obj.test_convert_gray_to_rgb() without return types